Mornings on Horseback by David McCullough traces the early life of Theodore Roosevelt, Jr. McCullough examines Theodore's love of the outdoors, his health problems, and his family relations. He also discusses Theodore's time at Harvard University, his first marriage, and his entrance into politics. These experiences helped shape and influence Roosevelt's later years, as President of the United States and other political positions.

Theodore Roosevelt's childhood was characterized by a loving and involved family and health problems. He grew up in a privileged household, the son of Theodore, Sr. and Mittie Roosevelt. He had one older sister, Bamie, a younger brother, Elliott, and a younger sister, Corinne. The family was drawn together, in part, because of Teedie's asthma attacks.

The young Teedie loved the outdoors, and the freedom and interest it provided. The family spent a year abroad on a Grand Tour of Europe. They also spent some time later traveling on the Nile River. Summers were spent in the country and at Oyster Bay. As a young adult, Teedie collected bird and animal specimens, doing his own taxidermy.

Teedie attended Harvard University in the late 1800s. He resided off campus in quarters that Bamie choose and furnished for him. His years at Harvard were happy ones for the most part, although marred by the death of his father. During his junior and senior years, he bloomed socially, and enjoyed attending parties and other gatherings.

While at Harvard, Theodore, Jr. met Alice Lee, whom he proposed to. They were married Oct. 27, 1880, several months after Theodore graduated from Harvard. The couple moved into the family's home in New York with Mittie. This happy arrangement was to be short-lived, however. On Feb. 12, 1884, Alice gave birth to a baby girl, but on Feb. 14, Mittie and Alice both died suddenly. Mittie succumbed to typhoid fever, and Alice died from Bright's disease. Theodore would remarry several years later.

Theodore's early political career was eventful and helped pave the way for his later positions. He was elected to the New York State Assembly in the early 1880s. There, he quickly established himself as a force to be reckoned with. Similarly, he received quite a bit of attention at his first Republican National Convention, when he supported another nominee instead of the frontrunner, Blaine.

Roosevelt's life also brought him to the West, a place that would inspire him and be a focus of his later writing. He first went west in 1883 and, over the next several years, he would spend extended periods of time there, particularly after Alice's death. He bought several thousand head of cattle and built a house on a river in the Bad Lands.